So results are in, I added the inductor capacitor filter between the output of the MAX660 and the -5V plane and the 40KHz signal has been neutralized. I still have the 500KHz signal present but it is minimal in comparison to the noise present before. I could always add the LC filter to each line if I wanted to refine THIS design more.
I actually am looking into using the Active Twin-T Filter as suggested by Tony Stewart and I am going to use +12V and GND biasing the op-amps at half that, I already have the parts to breadboard and test. Thanks for that suggestion, you were right, the passband is so much flatter and the notch is very fine. .
At this point, I am going to add the LC filter to the existing and redesign the next revision using the Twin-T Notch, so this discussion can be closed by a Moderator as far as I am concerned.
I want to personally thank you all for your expertise and valuable input as you've done an excellent job in helping this newbie.
-Bruce